I disagree.
Electronic Music isn't the only one to do this.
Rock music does this as well. They separate different styles into many sub-genres.
Nu Metal, Metal, Heavy Metal, Rock, Rock and Roll, Indie Rock, Grunge, Progressive Rock, Krautrock, Math Rock, Surf Rock, Skate rock, Death Metal, Black Metal, Goregrind, Grindgore, Pornogrind, Punk, Punk Rock, Post Punk, Indie Punk, Pop Punk, Pop Rock, Alternative Rock, (we could go on like this all day man)
Steffeeh has an interesting point imo.
I do agree that electronic music fans might take it a little too far. I think the main-main genres are Dubstep, House, Ambient, Chill-Out, Trance, DnB, Breakbeat, Industrial, Techno, and Chill-wave/Chill-step. Everything else are just the sub-genres.